This invention relates to pressurized air operated hydraulic equipment, and more particularly to an air-hydraulic pump.
As is known, an air-hydraulic pump delivers hydraulic fluid pressure in response to a supply of pressurized air. Air-hydraulic pumps are well known and used in many applications, one of which is to provide fluid pressure to an expander for expanding a pipe or the like. Such a tool is commonly employed to expand the end of a cut-off exhaust pipe for installing a replacement muffler in the exhaust system of an automobile by connection to the exhaust pipe. In applications such as this, it is necessary for the air-hydraulic pump to deliver a high level of pressure to the pipe expander in order to overcome the large load placed thereon by the unexpanded pipe.
Prior art air-hydraulic pumps deliver a constant amount of pressure to a hydraulic system, regardless of the load on the system. As a result, in a pump designed to deliver high fluid pressure, the flow rate or volume of hydraulic fluid pumped through the system is relatively low. Such low volume, high pressure pumping of fluid results in a relatively slow speed of operation of the expanding tool. In some instances, for example when the stem of the expanding tool must be withdrawn a certain amount prior to causing the expandable sleeve to make contact with the inner surface of the pipe, such slowness of operation results in wasted time of the operator and an overall inefficient operation. Further, such an operation is typically performed overhead, and maintaining the expander in position for an extended period of time is a difficult task, due to the weight of the expander.
Other applications of an air-hydraulic pump entail the same or similar inefficiencies of operation resulting from slow movement of a hydraulically operated member which requires a high level of pressure in order to perform its task.
The present invention addresses the above-noted problem in operation of an air-hydraulic pump, and provides a means for reducing the amount of time necessary for the work-performing element of the hydraulic system to attain a certain predetermined level of load thereon which requires a relatively high level of hydraulic pressure delivered to the work-performing element for overcoming such load. The present invention provides an air-hydraulic pump having relatively high, level of pressure to the work-performing element of the hydraulic system for overcoming the predetermined load exerted thereon. As discussed above, the high level of pressure results in a low flow rate of fluid through the system. The invention provides an auxiliary pumping means for delivering a second, relatively low, level of pressure to the work-performing element at a relatively high flow rate for increasing the speed at which the work-performing element operates prior to exertion of the predetermined load thereon. Once the predetermined load is exerted on the system, the auxiliary pumping means ceases operation due to exertion of the predetermined load on the system, and the primary pumping means then delivers the first level of pressure to the system in order to overcome the predetermined load.
In one embodiment, the primary pumping means comprises a piston having a head and a rod, with the head being selectively exposed to pressurized air through a control means for providing reciprocating movement of the piston. Such reciprocating movement of the piston rod provides pumping of hydraulic fluid by the piston rod end for delivering a high level of hydraulic pressure to the system at a relatively low volume. The auxiliary pumping means preferably comprises a floating ring, or floating piston, slidably mounted to the piston rod and having a hydraulic fluid contact surface and a surface exposed to pressurized air. The hydraulic fluid contact surface provided on the floating ring is greater than the hydraulic fluid contact surface of the piston rod end. Through the control means, reciprocating movement of the floating ring is provided for pumping fluid through the system at a relatively high flow rate, delivering a second level of fluid pressure to the system lower than the first level delivered by the reciprocating action of the rod end. When a predetermined level of load is exerted on the hydraulic system, the force exerted on the floating ring due to fluid pressure on the hydraulic fluid contact surface exceeds the force exerted on the ring by pressurized air on the surface of the floating ring exposed thereto, so that further reciprocating movement of the floating ring is prevented. In this situation, reciprocating movement of the piston continues, so that the piston rod end continues to deliver the first level of fluid pressure to the system.
The air-hydraulic pump of the invention preferably comprises an air intake block, a control block and a hydraulic block. A first cavity is preferably provided between the air intake block and the control block, within which the piston head is preferably disposed. A second cavity is preferably provided between the control block and the hydraulic block. The piston rod preferably extends through the control block and into the second cavity, within which the floating ring is preferably disposed. The hydraulic block includes passages with which the hydraulic system is in communication, so that hydraulic fluid pressure is provided therethrough to the system in response to reciprocating movement of the floating ring and/or the piston rod end.
The control means provided in the control block preferably includes means for selectively providing fluid pressure to the faces of the piston head or the surface of the floating ring exposed to pressurized air through the control means, for selectively providing reciprocating movement thereof. The control means preferably includes sensing means for detecting air pressure on the piston head faces, and means responsive to the sensing means for selectively providing pressurized air thereto and to the surface of the floating ring exposed to pressurized air through the control means for providing reciprocating movement of the piston head. The means responsive to the sensing means preferably comprises a series of passages formed in the control block in communication with one of the piston head faces and with the surface of the floating ring exposed to pressurized air, and passage means for providing pressurized air to the other face of the piston head. A spool member is mounted within a spool passage formed in the control block for reciprocating movement, to selectively provide pressurized air to such surfaces for reciprocating the piston and thereby providing fluid pressure in the hydraulic system.
The invention further provides a hand held work performing tool for use in connection with a hydraulic fluid system, with actuator means provided on the hand held tool for selectively providing pressurized air to the control means and thereby fluid pressure to the hydraulic system. The actuator means preferably comprises a normally closed air valve in communication with the supply of pressurized air, with the air valve being movable to an open position for providing pressurized air thereto and thereby operating the control means.